1. Field of the Invention
The present invention relates to an electro-photographic device, and more particularly to an electro-photographic device which is capable of controlling a paper feeding unit according to the result of a paper detecting examination.
2. Description of Related Art
In conventional electro-photographic devices, a toner tank for storing toner and a cartridge which houses a photo-sensitized drum for forming toner images are detachably provided on an upper cover, and the upper cover is attached to the main body of the device so that the upper cover shuts and opens. The photo-sensitized drum is connected to a paper feeding unit with a paper sending roller via a gear provided on the cartridge, and the paper sending roller rotates in synchronization with the photosensitized drum. Operators open the upper cover when they exchange a cartridge or remove printing paper from the electro-photographic device under a "paper jam" state, in which the device is unable to feed the printing paper.
The paper feeding unit is driven for a fixed period of time to recover synchronization in the gear connections when the upper cover is shut after a paper removal operation or a cartridge exchange operation.
In an electro-photographic device of the above description, a pair of fixation rollers, provided in the electro-photographic device for fixing toner images, cools during the paper removal operation or cartridge exchange operation. If the upper cover is shut with printing paper remaining in the device after the paper removal operation or the cartridge exchange operation, there is a possibility that the paper remaining in the device will be fed by the paper feeding unit and sent to the fixation rollers.
The surface of the fixation roller pair has a silicon film coating for preventing melting toner from adhering to the surface. When printing paper is sent to cold fixation rollers, the film on the surface is damaged by the toner, because the toner does not melt between the cold rollers. Consequently, the toner adheres to the damaged surface of the fixation rollers after the electrophotographic device resumes normal operation with the surface of the rollers set at the prescribed fixing temperature, resulting in defective printed images.